Why do people recommend separating drinking glasses that are stuck together by cooling the inner glass and heating the outer glass?

Question

I have seen mutliple people recommend this. Here is why it confused me:

If you had a large balloon stuck in the center of an inner-tube, and you wanted to separate them quickly, you would want both the baloon and the inner-tube to contract toward their centers.

If the baloon was slowly deflating (by losing air or cooling down), and you wanted it to stay stuck, you would want the inner-tube to inflate (by adding air or heating up) in order to keep its grip.

So, why are people recommending to expand one glass while shrinking the other? Won’t that just maintain the grip by the outer glass? Don’t we want to cool both glasses, so they both take up less space, creating air between them?

In: 0

Answer 1

I see what you are thing. You think that blowing up the inner tube will increase its width but not the length. This is not the case. If you let air out of the balloon no matter how much you inflate the inner tube it will not prevent the balloon from falling.

Also if you kept the balloon at the same inflation, inflating the tube will not squeeze it more but will loosen its grip.

This is the same as the glasses. The outer one will get bigger in inside diameter and loosen its grip.